31P NMR spectroscopy, together with histological analysis by lightand electron microscopy are used to detect structural andbiochemical heterogeneity within the normal human myometrium. Studies involve both SLIM analyses of whole or half uteri and highresolution spectroscopic analyses of small biopsy samples. Thesestudies are aimed both at providing a frame work forinterpretation of future results on gynecologic abnormalities andat gaining more insight into the role of the junctional zone ofthe